1.socket测试

要求：基于socket 基于TCP协议实现echo服务器（端口我们使用7+后三位学号）和客户端

客户端发送数据格式为：“客户端实现者8位学号：消息” 不符合规则的数据忽略，并提示出错。（5‘）

服务器响应消息格式是（10’）

“
客户端IP：XXXX
客户端PID：XXXX
服务器PID:XXXX
服务器实现者学号：XXXXXXXX
客户端内容发送内容倒序（比如：客户端发abc, 服务器返回cba）
”
注意服务器端要通过多进程实现，每次客户端链接到服务器，服务器就启动一个新进程程和客户端连接。（10‘）

代码：

Echo服务器代码（echo_server.c）：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>

#define PORT 7403

void handle_client(int client_socket) {
    char buffer[256];
    ssize_t bytes_read;

    // 读取客户端发送的数据
    bytes_read = read(client_socket, buffer, sizeof(buffer));
    if (bytes_read < 0) {
        perror("Error reading from socket");
        exit(1);
    }

    // 解析客户端发送的数据
    char student_id[9];
    char message[256];
    sscanf(buffer, "%8s:%[^\n]", student_id, message);

    // 检查数据格式是否正确
    if (strlen(student_id) != 8 || message[0] == '\0') {
        printf("Invalid data format from client\n");
        close(client_socket);
        exit(1);
    }

    // 获取客户端信息
    struct sockaddr_in client_address;
    socklen_t client_address_length = sizeof(client_address);
    getpeername(client_socket, (struct sockaddr*)&client_address, &client_address_length);
    char client_ip[INET_ADDRSTRLEN];
    inet_ntop(AF_INET, &(client_address.sin_addr), client_ip, sizeof(client_ip));
    pid_t client_pid = getpid();
    pid_t server_pid = getpid();

    // 将客户端发送的内容倒序
    int message_length = strlen(message);
    char reversed_message[message_length + 1];
    for (int i = 0; i < message_length; i++) {
        reversed_message[i] = message[message_length - i - 1];
    }
    reversed_message[message_length] = '\0';

    // 构建服务器响应消息
    char response[512];
    snprintf(response, sizeof(response),
             "客户端IP：%s\n"
             "客户端PID：%d\n"
             "服务器PID：%d\n"
             "服务器实现者学号：%s\n"
             "客户端内容发送内容倒序：%s\n",
             client_ip, client_pid, server_pid, student_id, reversed_message);

    // 发送响应消息给客户端
    ssize_t bytes_written = write(client_socket, response, strlen(response));
    if (bytes_written < 0) {
        perror("Error writing to socket");
        exit(1);
    }

    // 关闭客户端连接
    close(client_socket);
    exit(0);
}

int main() {
    int server_socket, client_socket;
    struct sockaddr_in server_address, client_address;
    socklen_t client_address_length;

    // 创建套接字
    server_socket = socket(AF_INET, SOCK_STREAM, 0);
    if (server_socket < 0) {
        perror("Error opening socket");
        exit(1);
    }

    // 设置服务器地址
    memset(&server_address, 0, sizeof(server_address));
    server_address.sin_family = AF_INET;
    server_address.sin_addr.s_addr = INADDR_ANY;
    server_address.sin_port = htons(PORT);

    // 绑定套接字到指定端口
    if (bind(server_socket, (struct sockaddr*)&server_address, sizeof(server_address)) < 0) {
        perror("Error binding socket");
        exit(1);
    }

    // 监听连接
    if (listen(server_socket, 5) < 0) {
        perror("Error listening on socket");
        exit(1);
    }

    while (1) {
        // 接受客户端连接
        client_address_length = sizeof(client_address);
        client_socket = accept(server_socket, (struct sockaddr*)&client_address, &client_address_length);
        if (client_socket < 0) {
            perror("Error accepting client connection");
            exit(1);
        }

        // 创建子进程处理客户端连接
        pid_t child_pid = fork();
        if (child_pid < 0) {
            perror("Error forking new process");
            exit(1);
        } else if (child_pid == 0) {
            // 子进程处理客户端连接
            close(server_socket);
            handle_client(client_socket);
        } else {
            // 父进程继续监听连接
            close(client_socket);
        }
    }

    // 关闭服务器套接字
    close(server_socket);

    return 0;
}

Echo客户端代码（echo_client.c）：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#define SERVER_IP "127.0.0.1"  // 服务器IP地址
#define SERVER_PORT 7403    // 使用端口号7+后三位学号

int main() {
    int client_socket;
    struct sockaddr_in server_address;

    // 创建套接字
    client_socket = socket(AF_INET, SOCK_STREAM, 0);
    if (client_socket < 0) {
        perror("Error opening socket");
        exit(1);
    }

    // 设置服务器地址
    memset(&server_address, 0, sizeof(server_address));
    server_address.sin_family = AF_INET;
    server_address.sin_port = htons(SERVER_PORT);
    if (inet_pton(AF_INET, SERVER_IP, &(server_address.sin_addr)) <= 0) {
        perror("Error converting server IP address");
        exit(1);
    }

    // 连接到服务器
    if (connect(client_socket, (struct sockaddr*)&server_address, sizeof(server_address)) < 0) {
        perror("Error connecting to server");
        exit(1);
    }

    // 构建客户端发送的数据
    char student_id[9] = "20211403";  // 请替换为自己的学号
    char message[256];
    printf("请输入消息：");
    fgets(message, sizeof(message), stdin);

    // 检查数据格式是否正确
    if (strlen(student_id) != 8 || message[0] == '\0') {
        printf("Invalid data format\n");
        close(client_socket);
        exit(1);
    }

    // 构建发送的数据
    char data[512];
    snprintf(data, sizeof(data), "%s:%s", student_id, message);

    // 发送数据给服务器
    ssize_t bytes_written = write(client_socket, data, strlen(data));
    if (bytes_written < 0) {
        perror("Error writing to socket");
        exit(1);
    }

    // 接收服务器响应
    char response[512];
    ssize_t bytes_read = read(client_socket, response, sizeof(response));
    if (bytes_read < 0) {
        perror("Error reading from socket");
        exit(1);
    }

    // 打印服务器响应
    printf("服务器响应：\n%s\n", response);

    // 关闭套接字
    close(client_socket);

    return 0;
}